The present invention relates to an electromagnetic contactor opened and closed in order to feed electric power to motors and so on, and in particular to an electromagnetic contactor that can be mounted even if an upper case is rotated by 180.degree. relative to a lower case.
FIG. 6 is a sectional view showing the configuration of a conventional electromagnetic contactor. A fixed iron core 6, and an electromagnetic coil 5 wound around a central leg of the fixed iron core 6 via a reel 3 are housed in an insulating lower case 2. An insulating upper case 1 is provided above the lower case 2, and a movable iron core 4 opposed to the upper end surface of the fixed iron core 6, a movable holder 8 operating in response to the movement of the movable iron core 4, and contacts opened and closed in response to the movement of the movable holder 8 are housed in the upper case 1. These contacts consist of two pairs of contacts laterally spaced apart from each other, and each pair consists of a movable contact 90A and a fixed contact 10A. The two movable contacts 90A are held by the movable holder 8 via a movable contact shoe 90, and are always urged downward by a contact spring 12.
On the other hand, the two fixed contacts 10A are fixed to the upper case 1 via fixing contact shoes 10. The two fixing contact shoes 10 are connected to main circuit terminal portions 21 disposed outside the upper case 1. In addition, the movable iron core 4 is always urged upward by a return spring 11. Furthermore, two coil terminal portions 9 (in FIG. 6, they are arranged in parallel in the rear direction) are provided on the right sides of the upper and lower cases 1 and 2, and are connected to starting and end conductors, respectively, of the electromagnetic coil 5 via feeding leads (not shown). The upper and lower cases 1 and 2 are connected together by wire springs 7, screws, or snap fits (not shown).
A switching mechanism of the electromagnetic contactor shown in FIG. 6 is described below. A power-side main circuit and a load-side main circuit (not shown) are connected to the right and left terminal portions 21, and a control power circuit (not shown) is connected to the coil terminal portions 9. In the configuration shown in FIG. 6, the contacts are open and no current flows between the right and left contact shoes 10. Under these conditions, when a control current is supplied to the coil terminal portions 9 from the control power circuit, the electromagnetic coil 5 is excited and the fixed iron core 6 attracts the movable iron core 4 against the force of the return spring 11. Accordingly, the movable holder 8 moves downward, so that the movable contact shoe 90 also moves downward to contact the movable contacts 90A with the fixed contacts 10A. Thus, the two fixed contact shoes 10 are shorted via the movable contact shoe 90 to close the main circuit. With the electromagnetic contactor in the closed state, the contact spring 12 urges the movable contact shoe 90 downward to maintain the pressure between the contacts, thereby constantly maintaining good contact conditions.
Next, with the electromagnetic contactor in the closed state, when the excitation of the electromagnetic coil 5 is shut off, the return spring 11 moves the movable iron core 4 upward. The movable contact shoe 90 simultaneously moves upward via the movable holder 8 to release the movable contacts 90A from the fixed contacts 10A, thereby opening the contacts. Thus, the two fixed contact shoes 10 are separated to open the main circuit.
In the above conventional apparatus, however, the user may desire to rotate the electromagnetic coil terminal by 180.degree., and in this case, the electromagnetic contactor body must be rotated by 180.degree.. As a result, a name plate and a terminal number indication provided on the top surface of the upper case are reversed to confuse the operator during a wiring or inspecting operation.
Therefore, it is an object of this invention to enable the upper and lower cases to be attached to each other such that the upper case can be rotated by 180.degree. relative to the lower case.